Preparation and Photocatalytic Behaviors of Nanoporous Polyoxotungstate-Anatase TiO_2 Composites

Nanoporous anatase TiO2 crystalline particles coupled with Keggin or Wells-Dawson unit, H3PW12O40/TiO2 or H6P2W18O62/TiO2, were prepared at a low temperature （200℃ ） using sol-gel method combined with hydrothermal treatment at programmed temperature. The as-prepared composites have uniform anatase phase, and they exhibit both micrand mesoporosities with pore sizes of 0.6 and 4.0 nm, respectively, and their average size is lower than 10 nm. Photocatalytic tests show the composites exhibit relatively higher photocatalytic activities to decompose the organocholorine pesticide hexachlorobenzene（HCB） than anatase TiO2, the starting polyoxotungstates, and EuEOa/TiO2 prepared by using sol-gel method, and this was attributed to （ 1 ） the synergistic effect of photoactive anatase TiO2 with the polyoxotungstate, and （2） the fascinating physical and chemical properties of the porous materials.

Hydrothermal Synthesis and Structure of a Mixed-valence Polyoxotungstate Decorated by Copper(I) Coordination Group, [Cu(en)_2H_2O]_2[{Cu(en)_2}HPW_(12)O_(40)]·2H_2O

A complex [Cu(en)2H2O]2[{Cu(en)2}HPW12O40]?2H2O (C12H57Cu3N12O44PW12, Mr = 3501.49) has been synthesized under hydrothermal conditions and its crystal structure was determined by X-ray diffraction. It crystallizes in the orthorhombic system, space group Pbca with a = 21.680(4), b = 20.680(4), c = 26.120(5) ?, V = 11711(4) ?3, Dc = 3.972 g/cm3, Z = 8, μ(MoKa) = 24.661 mm?1, F(000) = 12440, the final R = 0.0527 and wR = 0.1416 for 11527 observed reflec- tions with I > 2σ(I). The crystal structure is composed of [{Cu(en)2}HPW12O40]2? anions, discrete [Cu(en)2H2O]+ complex cations and crystal water molecules, which are held together into a three- dimensional network through hydrogen-bonding interactions. The anionic [{Cu(en)2}HPW12O40]2? is formed by the mixed valance {HPWVI11WVO40}3? Keggin unit covalently linked by a {Cu(en)2}+ group.

Synthesis and Spectroscopic Characterization of Organothiophosphoryl Polyoxotungstates α-[C_6H_(11)P(S)]_2X^(n+)W_(11)O_(39)^((8-n)-)(X^(n+)P^(5+), Si^(4+), Ge^(4+), Ga^(3+)

Organothiophosphoryl polyoxotungstate derivatives α-C_6H_(11)P(S)]_2X^(n+)W_(11)O_(39)^((8-n)-)(X=P, Si, Ge, Ga) were obtained by the reactions of the monovacant α-_2X^(n+)W_(11)O_(39)^((8-n)-)(X=P, Si, Ge, Ga) were obtained by the reactions of the monovacant α-[X^(n+)W_(11)O_(39)]^((12-n)-)(X=P, Si, Ge, Ga) anions with electrophilic C_6H_(11)P(S)Cl_2 in acetonitrile. These new organic-inorganic hybrid anions were characterized by elemental analyses, IR, (()^(31)P) and (()^(183)W) NMR spectrometries. The six-line ()^(183)W NMR spectrum indicates that [C_6H_(11)P(S)]_2X^(n+)W_(11)O_(39)^((8-n)-)(X=P, Si, Ge, Ga) anions possess true C_s symmetry in acetonitrile. According to the spectroscopic observation and the chemical analyses, it is known that each of the hybrid anions consists of an α-[XW_(11)O_(39)] framework on which two equivalent C_6H_(11)P(S) groups are grafted through P-O-W bridges.

A Novel 3D Polyoxotungstate Constructed from Dawson Polyanions and Alkaline Earth Cations

A novel 3D polyoxotungstate [Ca（H2O）2][Ca（H2O）3]H2[P2W18O62]·9H2O（1） has been synthesized by the conventional aqueous solution method and characterized by IR spectrum,elemental analyses,single-crystal X-ray diffraction and electrochemistry.1 crystallizes in triclinic,space group P1 with a = 12.9077（14）,b = 14.8593（16）,c = 20.023（2）,α = 70.1620（10）,β = 80.8110（10）,γ = 64.3770（10）o,V = 3256.9（6）3,Z = 2,Dc = 4.790 g/cm3,μ = 31.975 mm-1,F（000） = 4080,R = 0.0412,and wR = 0.1039.X-ray single-crystal structural analysis indicates that the molecular structural unit of 1 consists of one saturated Dawson [α-P2W18O62]6-polyanion,one seven-coordinate [Ca（H2O）2]2＋ cation,one eight-coordinate [Ca（H2O）3]2＋ cation,two protons and nine lattice water molecules.Interestingly,adjacent Dawson [α-P2W18O62]6-polyanions are connected by [Ca（H2O）2]2＋ and [Ca（H2O）3]2＋ cations and hydrogen bonding interactions to form a 3D infinite framework.The electrochemistry property of 1 has been studied.

Synthesis, Crystal Structure and Photocatalytic Properties of a Supramolecular Assembly Based on Keggin Polyoxotungstate

A new supramolecular compound （4,4＇-bipyH）4[SiW12O40]（4,4＇-bipy） （4,4＇-bipy = 4,4＇-bipyridine） was synthesized hydrothermally and characterized by single-crystal X-ray diffraction and IR spectrum. The crystallography analysis for the title compound reveals that the crystal crystallizes in monoclinic, space group C2/m with a = 22.2767（12）, b = 21.1879（11）, c = 15.6942（8） A, β = 97.068（3）°, V = 7351.3（7） A3, Cs0H44N10040SiW12, Mr = 3659.24, Z = 4, Dc = 3.306 g/cm3, F（000） = 6544, GOOF = 1.137, R = 0.0577 and wR = 0.1579. The title compound consists of a discrete Keggin-type [SiWl2O40]4- anion, one 4,4＇-bipy and four protonated （4,4＇-bipyH）＋ cations. The [SiWl2O40]4- anion and protonated 4,4＇-bipy are connected to form a supramolecular structure by hydrogen bonds. Meanwhile, the title compound exhibits good photocatalytic activity for color degradation of Rhodamine-B dye solution under visible-light irradiation.

Comparison of Catalytical and Biological Activities for Substituted Polyoxotungstates Containing Ti and CpTi

The effect of the functionallization of POMs on their properties was examined by the comparison between both titanium and its corresponding cyclopentadienyl subsituted polyoxocomplexes. The polarographic half wave potential of the complexes indicated that the effect of the functionallization of POMs increased the oxidizing ability of the polyoxoanions. The inhibitory effects of the CpTi polyoxocomplexes on tumor cells are higher than those of the corresponding titanium polyoxocomplexes, and the toxicity of the former is lower than that of the latter. The oxygenation reactions of cyclohexene, styrene, trans stilbene and maleic acid with PhIO or hydrogen peroxide(30% aqueous solution) catalyzed respectively by Ti and CpTi polyoxocomplexes were compared.

Synthesis and Structural Characterization of One New Polyoxotungstate Connected via Potassium Cations with aThree-dimensional Framework: H_6Na_2K_4(H_2W_(12)O_(42))Cl_2·14H_2O

One new polyoxotungstate complex H6Na2K4（H2W12O42）Cl2·14H2O 1 has been prepared in the beaker solution and characterized by elemental analysis and IR spectroscopy. Crystal data： H36Cl2K4W12Na2O56, Mr = 3411.77, monoclinic, space group P21/c, a = 11.5734（16）, b = 14.3136（19）, c = 15.459（2）A, β = 105.601（2）°, V = 2466.5（6）A^3, Z = 2, Dc = 4.594 g/cm^3, F（000） = 3008, μ = 28.447 mm^-1, R = 0.0574 and wR = 0.1239 （Ⅰ〉 2σ（Ⅰ））. Single-crystal X-ray diffraction analysis results reveal that a three-dimensional architecture in the title compound is constructed from the H2W12O42^10- units linked by potassium.

Comparing the Structures of Two Allomorphic Polyoxotungstates and the Difference in Weak Interactions by Thermal-dependent 2D-COS IR to Identify

A three-dimensional （3D） Keggin-type heteropolytungstate{Zn（phen）3}3[ZnW12O40]·9H2O 1 （phen = 1,10-phenanthroline） has been synthesized through a conventional hydrothermal synthesis and was characterized by X-ray single-crystal diffraction analysis, X-ray powder diffraction （XRD）, IR, UV-DRS, thermogravimetric analysis （TGA）, thermal-dependent 2D-IR correlation spectroscopy （2D-COS IR） and Raman spectrum. Crystal data for compound 1： trigonal system, space group R3 with a = b = 25.268（4）, c = 17.462（5） A, ）, = 120°, V= 9655（4） A3 and Z = 3. Compound 1 is allomorphic to {Co（phen）3}3[CoW12O40]·9H2O 2, which has been reported by Feng Chai et al. In compound 2, its prominent feature is that the decisive role of water molecules （O-H…O） builds a 3D supramolecular structure. However, in the structure of compound 1, the interlayer space is filled by Zn（phen）3]2＋ cations which linked the layers via C-H…O hydrogen bonding interactions to construct a three-dimensional framework. Two compounds are different in weak interactions, so we identify them by Thermal-dependent 2D-COS IR. Moreover, the fluorescence of compound 1 was also described.

A New Heteropolyoxotungstate with a Three-dimensional All-inorganic Framework [(C_2H_4N_2)_4(P_4Co_3W_4O_(28)H_6)(H_2C_2O_4)]_n

A new heteropolyoxotungstate [（C2H4N2）4（P4Co3W4O28H6）（H2C2O4）]n with a three-dimensional framework was hydrothermally synthesized.The compound crystallizes in a tetragonal system,space group I41/a with a = 17.1006（17）,b = 17.1006（7）,c = 10.7525（5）,V = 3144.2（2）3,Z = 4,Dc = 3.795 g·cm-3,F（000） = 3300,MoKα（λ = 0.71073 ）,μ = 16.460 mm-1,the final R = 0.0335 and wR = 0.0776.In the heteropolyoxotungstate,tungsten-oxygen octahedra are linked by sharing two cis-vertexes into an infinite helical chain extending along the c axis.Cobalt atoms in the octahedral geometry act as the linkers of these chains,forming a three-dimensional framework.The cobalt and phosphorus atoms in the tetrahedral geometry play a role in stabilizing the three-dimensional framework.Ethylenediamine molecules are polymerized into organic chains which locate in the interspaces of the framework in the way of interwinding with the W-O chains.

Giant Ln_(30)-Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

Although the synthesis of giant lanthanide(Ln)-containing polyoxotungstates(POTs)has long been actively pursued,it remains challenging to encapsulate high-nuclearity Ln–O clusters in POT shells because of the highly complicated assembly process.This work demonstrates a simple synthetic strategy of using lacunary POT precursors to assemble with in situ generated Ln–O clusters in the presence of basic N-containing ligands,which exert a slow-releasing effect for Ln^(3+)ions in alkaline conditions.

Multicomponent Cooperative Assembly of Nanoscale Boron-Rich Polyoxotungstates with 22 and 30 Boron Atoms

This work demonstrates that the introduction of positive lanthanide(Ln)and transition metal(TM)cations into polyoxotungstates(POTs)to stabilize negative oxoboron clusters is a feasible and general synthetic strategy for creating not only rare boron-rich POTs but also intriguing multicomponent composite polyoxometalates(POMs).By this strategy,a large family of unprecedented boron-rich POTs with 22 and 30 boron atoms,such as[(B_(18)Si_(3)Ln_(6)O_(36)(OH)_(14)){B_(4)Ni_(4)O_(10)(OH)_(4)(A-α-SiW_(9)O_(34))}_(3)]^(44−)(1Ln),[(B_(19)Si_(2)Ln_(7)O_(35)(OH)_(15)(H_(2)O)){B_(4)Ni_(4)O_(10)(OH)_(4)(A-α-SiW_(9)O_(34))}_(2){B_(3)Ni_(4)O_(9)(OH)_(3)(A-α-SiW_(9)-O_(34))}]^(41−)(2Ln),where Ln is Gd,Tb,and Dy,and[(B_(22)O_(42)){LnNi_(3)(OH)_(3)(B-α-SiW_(9)O_(34))}_(4)]^(34−)(3Ln;Ln is Sm,Gd,and Tb),have been obtained.These POTs incorporate the largest number of boron atoms and the highest-nuclearity oxoboron clusters of any molecular POTs reported to date.The results show the fusion of two distinct research areas of POT chemistry and oxoboron cluster chemistry.In addition,they also show a family of unique POMs made from multiple oxo clusters including W-O,B-O,TM-O,and Ln-O.Experiments indicate these novel composite materials can exhibit effective catalytic activity for oxidizing toxic 2-chloroethyl ethyl sulfide.

A Novel 5-Fluorouracil Salt of 12-Silicatungstic Acid: Synthesis,Structure Characterization and Antitumor Activity

A novel 5-fluorouracil salt of 12-silicatungstic acid was synthesized and characterized by means of elemental analysis, IR, 1H NMR and 183W NMR spectra. The antitumor activity and toxicity of the complex have been evaluated both in vitro and in vivo.

Hydrothermal Synthesis and Crystal Structure of a Novel Composite Keggin-type Arsenotungstate: [Ni(phen)_2][Hphen](AsW_(12)O_(40))

A novel polyoxometalate-based composite compound [Ni（phen）2][Hphen]（AsW12040） （phen = 1,10-phenanthroline） I has been hydrothermally synthesized and characterized by elemental analysis, IR, TGA, ESR spectroscopy and single-crystal X-ray diffraction. Each structure unit of 1 consists of one polyoxoanion AsW12O40^3-, one free phenanthroline molecule and one coordination cation [Ni（phen）2]^2＋. The title compound crystallizes in the orthorhombic system, space group F212121, with a = 12.2383（7）, b = 21.0884（11）, c = 22.3237（12） A, V= 5761.4（5） A^3, Mr = 3520.44, Z = 4, Dc = 4.059 g/cm^3, F（000） = 6204, g（MoKα） = 24.844 mm^-1, GOF = 1.022, the final R = 0.0376 and wR = 0.0742 （I 〉 2σ（I）） for 865 parameters and 9637 observed reflections with I 〉 2σ（I）.

Photocatalytic Hydrogen Evolution of Keggin-type Polyoxo-tungstates and their Electrochemical Behaviors

The photocatalytic hydrogen evolution and electrochemical behaviors of Kiggen-type XW12O40^n- （X=P, Ge and Si） are investigated. It is found that the two-electron reduced species are active for H^＋ reduction and the more negative the potential of XW12O40^（n＋2）-/（n＋1）- is, the higher the activity for hydrogen evolution is.

Synthesis, Structure and Characterization of [Cu(2,2′-bpy)_2][{Cu(2,2′-bpy)_2}_2W_(12)O_(40)(H_2)]·4H_2O

An organic-inorganic compound [Cu（2,2＇-bpy）2][{Cu（2,2＇-bpy）2}2W12O40（H2）]·4H2O （Mr = 4048.00） was prepared from the hydrothermal reaction of Na2WO4.2H2O, CuC12·2H20, 2,2＇-bipyridine （2,2＇-bpy） and H2O at 160 ℃ for 4 days. The compound crystallizes in the monoclinic system, space group P21/n with a = 18.9196（8）, b = 20.4212（8）, c = 21.8129（9）A, β = 96.992（3）^o, V= 8365.0（6）A3, Dc= 3.214 g/cm^3, Z = 4μ（MoKct） = 17.269mm^-1 and F（000） = 7324. Of the 119837 total reflections, 17315 were unique （Rint = 0.0489）. The final R = 0.0385 and wR = 0.0770 for 11142 observed reflections with I 〉 2a（I）. Single-crystal X-ray diffraction reveals that the structure is composed of [（Cu（2,2＇-bpy）2}2W12040（H2）]^2- anions, discrete [Cu（2,2＇-bpy）2]^2＋ cations and lattice water molecules, and the anion is made up of a {W12O40（H2）}^6- α-Keggin core decorated with two [Cu（2,2＇-bpy）2}^2＋ groups through bridging oxygen atoms.

Hydrothermal Synthesis and Structure of One New Polyoxotungsate [Ni(trien)]_4[Ni_4(H_2O)_2(HPW_9O_(34))_2]·4H_2O

One new sandwich-type tetra-nickel substituted polyoxotungsate,[Ni（trien）]4-[Ni4（H2O）2（HPW9O34）2]·4H2O（1,trien=triethylenetetramine）,has been hydrothermally synthesized and characterized by IR,elemental analysis,TGA,and single-crystal X-ray diffraction analysis.Crystal data for 1：triclinic,space group P with a=13.279（3）,b=13.816（3）,c=14.494（4）,α=95.403（1）,β=113.173（4）,γ=93.809（3）o,V=2418.0（10）3,Z=1 and Dc=3.861 g/cm3.X-ray crystallographic study shows that compound 1 is a relatively rare inorganic-organic hybrid polyoxo tungstate constructed from sandwich Ni-substituted polyoxo-anions and nickel complexes.

A unique organic-inorganic hybrid Fe^(Ⅲ)–Pr^(Ⅲ)-included 2-germano-20-tungstate and its electrochemical biosensing properties

An organic-inorganic hybrid Fe^(Ⅲ)–Pr^(Ⅲ)-included 2-germano-20-tungstate[Pr(H_(2)O)_(8)]2 H_(2)[Fe_(4)(H_(2)O)_(4)(pca)_(4) Ge_(2)W_(20)O_(72)]•34H_(2)O(Hpca=2-pyridinecarboxylic acid)(1)was hydrothermally prepared.Its polyoxoanion comprises one tetra-Fe^(Ⅲ)incorporated[Fe_(4)(H_(2)O)_(4)(pca)_(4) Ge_(2)W_(20)O_(72)]^(8-)hybrid entity and two[Pr(H_(2)O)_(8)]^(3+)ornamental cations.The[Fe_(4)(H_(2)O)_(4)(pca)4 Ge_(2)W_(20)O_(72)]^(8-)2-germano-20-tungstate entity can be regarded as an infrequent S-type[Ge_(2)W_(20)O_(72)]^(16-)cluster pocketed by four[Fe(H_(2)O)(pca)]2+cations.The S-type[Ge_(2)W_(20)O_(72)]16-cluster could be imagined as condensation of two divacant Keggin[α-GeW _(10)O_(37)]^(10-)segments by sharing two atoms.It is of interest is that carboxyl O and pyridine N atoms on pca ligands concurrently bind with Fe ^(3+)cations in a five-membered heterocyclic fashion to increase the stability of the whole structure.Furthermore,the electrochemical biosensing properties of 1 as the modified electrode material have been investigated for detecting norepinephrine(NPP),showing a low detection limit of 3.25μmol/L.This work not only enriches structures of heterometallic german-otungstates(GTs),but also expands applications of polyoxometalates(POMs)in the electrochemical biosensing field.